Autonomous Driving Control Method and Autonomous Driving Control Device

ABSTRACT

An autonomous driving control method for stopping a host vehicle such that an inter-vehicle distance to a preceding vehicle is a predetermined at-stopping inter-vehicle distance includes: executing first stop control of setting the at-stopping inter-vehicle distance to a first at-stopping inter-vehicle distance shorter than a predetermined basic at-stopping inter-vehicle distance when a stop position of the host vehicle is within a forward stop limit area set in front of a crossing lane, and/or executing second stop control of setting the at-stopping inter-vehicle distance to a second at-stopping inter-vehicle distance longer than the basic at-stopping inter-vehicle distance when the stop position of the host vehicle is within a rearward stop limit area set behind the crossing lane.

TECHNICAL FIELD

The present invention relates to an autonomous driving control methodand an autonomous driving control device.

BACKGROUND ART

JP2015-147525A proposes, in order not to stop a host vehicle in anintersection, driving support control in which an inter-vehicle distanceto a preceding vehicle is set to be longer than an intersection roadlength (distance from an intersection entrance to an intersection exit)when an arrival distance to the intersection is equal to or less than apredetermined value.

SUMMARY OF INVENTION

When stopping the host vehicle based on the driving support control inJP2015-147525A, it is assumed that there is a possibility that,depending on a stop position, other vehicles are prevented fromdeparting from the intersection and the other vehicles are left in theintersection.

In view of such circumstances, an object of the present invention is toprovide an autonomous driving control method and an autonomous drivingcontrol device that can suppress other vehicles from being left in anintersection, in particular, in a crossing lane in which a travelingroad, a line, a sidewalk, or the like intersects with a traveling roadon which a host vehicle travels.

According to an aspect of the present invention, an autonomous drivingcontrol method for stopping a host vehicle such that an inter-vehicledistance to a preceding vehicle is a predetermined at-stoppinginter-vehicle distance is provided. The method includes: executing firststop control of setting the at-stopping inter-vehicle distance to afirst at-stopping inter-vehicle distance shorter than a predeterminedbasic at-stopping inter-vehicle distance when a stop position of thehost vehicle is within a forward stop limit area set in front of acrossing lane, and/or executing second stop control of setting theat-stopping inter-vehicle distance to a second at-stopping inter-vehicledistance longer than the basic at-stopping inter-vehicle distance whenthe stop position of the host vehicle is within a rearward stop limitarea set behind the crossing lane.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a vehiclecontrol system commonly applied to embodiments of the present invention.

FIG. 2 is a flowchart illustrating an autonomous driving control methodaccording to a first embodiment.

FIG. 3 is a diagram illustrating an example of a specific scene to whichfirst stop control is applied.

FIG. 4 is a diagram illustrating an example of a specific scene to whichsecond stop control is applied.

FIG. 5 is a flowchart illustrating an autonomous driving control methodaccording to a second embodiment.

FIG. 6 is a flowchart illustrating an autonomous driving control methodaccording to a third embodiment.

FIG. 7 is a flowchart illustrating first stop control according to afourth embodiment.

FIG. 8 is a flowchart illustrating an autonomous driving control methodaccording to a fifth embodiment.

FIG. 9 is a diagram illustrating an example of a specific scene in whichexecution of priority switching processing is assumed.

FIG. 10 is a diagram illustrating an example of a map for defining arelationship between the number of vehicles in an intersection and acorrection target inter-vehicle distance to be set in an autonomousdriving control method according to a sixth embodiment.

FIG. 11 is a flowchart illustrating an autonomous driving control methodaccording to a seventh embodiment.

FIG. 12A is a diagram illustrating modification 1.

FIG. 12B is a diagram illustrating modification 2.

FIG. 12C is a diagram illustrating modification 3.

FIG. 12D is a diagram illustrating modification 4.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings and the like. The term “autonomous driving” inthe present description is a concept that includes both operationcontrol of a vehicle that supports a part of a driving operation by adriver of the vehicle (autonomous driving level = 1 to 4), and operationcontrol of the vehicle without an operation by the driver (autonomousdriving level = 5). In addition, the term “forward” in the presentdescription means a forward in a traveling direction of a vehicle(hereinafter referred to as a “host vehicle α”) on which autonomousdriving control methods according to the embodiments are to be executed(traveling direction designated by a traveling lane L1 of the hostvehicle a). Further, the term “rearward” means a rearward in thetraveling direction of the host vehicle a on which the autonomousdriving control methods according to the embodiments are to be executed.Therefore, in front of or behind a crossing lane Ct, which will bedescribed later, is not universally determined, and is appropriatelydetermined according to the traveling direction of the host vehicle a(the host vehicle a is traveling in the traveling lane L1 or in a lanefacing the traveling lane L1).

System Configuration Common to Embodiments

FIG. 1 is a diagram illustrating a configuration of a vehicle controlsystem 10 commonly applied to the embodiments.

As illustrated, the vehicle control system 10 includes an externalsensor 1, an internal sensor 2, a navigation system 3, a communicationinterface 4, an actuator 5, a display 6, and a controller 20. Thevehicle control system 10 is mounted on a vehicle (hereinafter referredto as a “host vehicle α”) on which an autonomous driving control methodaccording to the present embodiment is to be executed.

The external sensor 1 is a detection device that detects a surroundingsituation of the host vehicle a. In particular, the external sensor 1includes an in-vehicle camera 1 a and a radar 1 b.

The in-vehicle camera 1 a is an imaging device that images a surroundingof the host vehicle α. The in-vehicle camera 1 a is provided, forexample, on a vehicle interior side of a windshield of the host vehicleα. The in-vehicle camera 1 a includes a monocular camera or a stereocamera. The in-vehicle camera 1 a outputs an imaged surrounding image ofthe host vehicle a to the controller 20.

The radar 1 b detects an object such as another vehicle present outsidethe host vehicle a using radio waves. The radio waves are, for example,millimeter waves. More specifically, the radar 1 b transmits radio wavesto the surrounding of the host vehicle α, receives radio waves reflectedby an object, and detects the object. The radar 1 b can output, forexample, a distance or a direction to the object as object information(in particular, surrounding vehicle information). The radar 1 b outputsdetected surrounding vehicle detection data to the controller 20.Instead of or in addition to the radar 1 b, laser imaging detection andranging (LIDER) that detects the object outside the host vehicle a usinglight may be mounted as the external sensor 1.

The internal sensor 2 is a detector that detects various types ofinformation according to a traveling state of the host vehicle a. Forexample, the internal sensor 2 includes a vehicle speed sensor thatdetects a vehicle speed of the host vehicle a (hereinafter also referredto as a “host vehicle speed Va”), an acceleration sensor that detects anacceleration of the host vehicle α, and the like.

The navigation system 3 is a device that obtains traveling routeinformation to a destination set on a map by an occupant such as adriver of the host vehicle α, and outputs the traveling routeinformation to the controller 20. More specifically, the navigationsystem 3 obtains a traveling route set for the host vehicle a as targetroute information based on position information of the host vehicle ameasured by a global positioning system (GPS) and map information in apredetermined map database. The map information may include an HD map(dynamic map) including information on road conditions such as thenumber of lanes or a shoulder size, traveling amount of other vehicles,presence or absence of an obstacle, or the like, in addition toinformation on a travelable path.

The communication interface 4 includes various communication protocolsfor receiving information necessary for traveling of the host vehicle aand information pointed out by the occupant from a predeterminedexternal server and transmitting the information to the controller 20.The communication interface 4 is implemented by, for example, vehicle tovehicle (V2V) that enables communication between the controller 20 andanother vehicle (vehicle-to-vehicle communication), vehicle toinfrastructure (V2I) that enables communication between the controller20 and infrastructure equipment such as a traffic light (road-to-vehiclecommunication), and vehicle to network (V2N) that enables communicationbetween the controller 20 and a predetermined external server (includinga cloud).

The actuator 5 is a device for operating the host vehicle a to atraveling state according to a command from the controller 20. Inparticular, the actuator 5 includes a drive actuator 5 a, a brakeactuator 5 b, and a steering actuator 5 c.

The drive actuator 5 a is a device for adjusting a drive force of thehost vehicle a. In particular, when the host vehicle a is mounted withan engine as a traveling drive source, the drive actuator 5 a includes athrottle actuator that adjusts an amount of air supplied to the engine(throttle opening degree) or the like. On the other hand, when the hostvehicle a is a hybrid vehicle or an electric vehicle in which a motor ismounted as a traveling drive source, the drive actuator 5 a includes acircuit (an inverter, a converter, or the like) capable of adjustingelectric power supplied to the motor.

The brake actuator 5 b is a device that adjusts a braking force actingon the host vehicle α. The brake actuator 5 b is implemented by aconfiguration (disc brake or the like) for obtaining the braking forceof the host vehicle a by a frictional force and/or a configuration(regenerative brake) for obtaining the braking force of the host vehiclea by a regenerative force of the motor mounted as a traveling drivesource.

The steering actuator 5 c includes an assist motor that controls asteering torque of an electric power steering system.

The display 6 is a device that is disposed in the vehicle interior anddisplays information based on a calculation result of the controller 20.The display 6 may be incorporated in a device equipped with a humanmachine interface (HMI) that receives an input (touch panel operation orthe like) from the occupant of the host vehicle α.

The controller 20 as an autonomous driving control device includes acomputer including a central processing unit (CPU), a read-only memory(ROM), a random access memory (RAM), and an input/output interface (I/Ointerface). The controller 20 is programmed to be capable of executingvarious processing in an autonomous driving control method to bedescribed later.

Functions of the controller 20 are implemented by an advanced driverassistance system (ADAS)/autonomous driving (AD) controller thatperforms main processing related to driving control of the host vehiclea or the like. The functions of the controller 20 may be implemented byany computer mounted on the host vehicle α, such as a motor controller,an engine control unit (ECU), or a vehicle control unit (VCU). Inaddition, the controller 20 may be configured by implementing a programon one piece of computer hardware, or may be configured to execute theautonomous driving control methods according to the embodiments byimplementing a program in which each processing is distributed on aplurality of pieces of computer hardware and integrating the pluralityof pieces of computer hardware.

In particular, the controller 20 performs various calculations forexecuting the autonomous driving control methods according to theembodiments by using various types of information received from theexternal sensor 1, the internal sensor 2, the navigation system 3, andthe communication interface 4 as inputs, displays a calculation resulton the display 6, and operates the actuator 5 based on the calculationresult.

More specifically, from a viewpoint of adjusting an inter-vehicledistance between the host vehicle a and a preceding vehicle β to apredetermined target inter-vehicle distance, the controller 20 operatesthe actuator 5 to execute following control of adjusting a differencebetween the host vehicle speed Va and a vehicle speed of the precedingvehicle β (hereinafter also referred to as a “preceding vehicle speedVβ”). Here, the target inter-vehicle distance is set to a predeterminedappropriate inter-vehicle distance from a viewpoint of safety andsuppression of overtaking of another vehicle. The target inter-vehicledistance may be a fixed value, or may be a variable value that variesaccording to the traveling state of the host vehicle a (host vehiclespeed Va, acceleration, or the like).

In particular, hereinafter, a target inter-vehicle distance at a timingat which the host vehicle a stops following the stop of the precedingvehicle β (timing at which both the host vehicle speed Va and thepreceding vehicle speed Vβ are zero) is referred to as an “at-stoppinginter-vehicle distance Dβ”.

The at-stopping inter-vehicle distance Dβ is set to an appropriate valuefrom a viewpoint of maintaining an appropriate inter-vehicle distance tothe preceding vehicle β in a stop state of the host vehicle a. Inparticular, in the following embodiments, an appropriate at-stoppinginter-vehicle distance Dβ according to various scenes is set to any oneof a “basic at-stopping inter-vehicle distance Dβ₀”, a “firstat-stopping inter-vehicle distance Dβ₁”, and a “second at-stoppinginter-vehicle distance Dβ₂”. Here, the basic at-stopping inter-vehicledistance Dβ₀ is set to an appropriate value (for example, about 5 m)from a viewpoint that the preceding vehicle β can be avoided by turningwhen the host vehicle a starts traveling from the stop state. Forexample, when an area where stopping is prohibited for legal or safetyreasons (stop prohibited area such as an intersection, a railroadcrossing, or an entrance of an emergency vehicle) is present between thepreceding vehicle β and the host vehicle α, from a viewpoint of avoidingthe area and stopping the host vehicle α, the basic at-stoppinginter-vehicle distance Dβ₀ can be set to a value larger than the valueat which the preceding vehicle β can be avoided by turning.

Hereinafter, the autonomous driving control methods according to theembodiments will be described in detail based on the aboveconfiguration.

First Embodiment

Hereinafter, an autonomous driving control method according to a firstembodiment will be described. In the present embodiment, a control modein which, after the host vehicle a is stopped in a state where theat-stopping inter-vehicle distance Dβ is set to the basic at-stoppinginter-vehicle distance Dβ₀, the stop position Pα of the host vehicle ais changed in order to facilitate retreating of the preceding vehicle βor a following vehicle γ from the crossing lane Ct will be described.

FIG. 2 is a flowchart illustrating the autonomous driving control methodaccording to the present embodiment. The controller 20 repeatedlyexecutes processing described below at each predetermined controlperiod.

First, in step S100, the controller 20 acquires various types of inputinformation. Specifically, the controller 20 acquires, as the inputinformation, information detected by the external sensor 1 (particularlyincluding the inter-vehicle distance between the host vehicle a and thepreceding vehicle β, the preceding vehicle speed Vβ, and the like),information detected by the internal sensor 2 (particularly includingthe surrounding image, the surrounding vehicle detection data, the hostvehicle speed Va, and the like), information obtained by the navigationsystem 3 (particularly including the position information of the hostvehicle α, the traveling route information, the HDD map, and the like),and information obtained by the communication interface 4 (particularlyincluding vehicle-to-vehicle communication information, road-to-vehiclecommunication information, and the like).

In step S101, the controller 20 causes the host vehicle a to stop at astop position Pα (hereinafter also referred to as a “basic stop positionPα₀”) based on the basic at-stopping inter-vehicle distance Dβ₀following the stop of the preceding vehicle β.

Next, in step S200, the controller 20 determines whether the stopposition Pα of the host vehicle a is within a forward stop limit areaR_(f) set in front of the crossing lane Ct.

Here, the crossing lane Ct in the present description means an areadefined as a merging portion of the traveling lane L1 on which the hostvehicle a travels and a traveling lane of a vehicle (including anautomobile, a tram, and a railroad vehicle) intersecting with thetraveling lane L1 (hereinafter also referred to as a “crossing travelinglane L2”). The crossing lane Ct includes a crosswalk along the travelinglane L1 and a crosswalk along the crossing traveling lane L2. Inaddition, the forward stop limit area R_(f) is an area extending over apredetermined range on an outer side in front of the crossing lane Ct inthe traveling lane L1 of the host vehicle a. In particular, when thestop position Pα of the host vehicle a is within the forward stop limitarea R_(f), the forward stop limit area R_(f) is set to a range in whichan advancing departure of the following vehicle γ from the crossing laneCt is considered to be blocked. Further, in the present embodiment, theforward stop limit area R_(f) is stored in advance in a storage areareadable by the controller 20. Considering that a length from the stopposition Pα of the host vehicle a to a rear end of a vehicle body variesdepending on a vehicle type or the like, an extension length of theforward stop limit area R_(f) may be appropriately adjusted according toa vehicle body size of the host vehicle a (in particular, vehicle lengthand vehicle width).

More specifically, the controller 20 determines whether the stopposition Pα is within the forward stop limit area R_(f) by referring tothe surrounding image, the surrounding vehicle detection data, knownvehicle body size data of the host vehicle α, and/or the HD map. Then,when it is determined that the stop position Pα is within the forwardstop limit area R_(f),the controller 20 executes first stop control instep S400.

In the first stop control in step S400, the controller 20 switches theat-stopping inter-vehicle distance Dβ to the first at-stoppinginter-vehicle distance Dβ₁ shorter than the basic at-stoppinginter-vehicle distance Dβ₀.

Here, the first at-stopping inter-vehicle distance Dβ₁ is a correctionvalue that is set to decrease and correct the basic at-stoppinginter-vehicle distance Dβ₀ from a viewpoint of changing the stopposition Pα forward (direction in which the inter-vehicle distance tothe preceding vehicle β is shortened) such that the stop position Pα isnot within the forward stop limit area R_(f). The first at-stoppinginter-vehicle distance Dβ₁ is preferably set to a length that does notexcessively shorten the inter-vehicle distance between the precedingvehicle β and the host vehicle a (for example, about ½ of the basicat-stopping inter-vehicle distance Dβ₀, while achieving an object ofpreventing the stop position Pα from being within the forward stop limitarea R_(f). Then, when the at-stopping inter-vehicle distance Dβ isswitched to the first at-stopping inter-vehicle distance Dβ₁, thecontroller 20 executes subsequent processing from step S700.

On the other hand, when it is determined in step S200 that the stopposition Pα is not within the forward stop limit area R_(f), thecontroller 20 executes processing in step S300.

In step S300, the controller 20 determines whether the stop position Pαis within a rearward stop limit area R_(r). Here, the rearward stoplimit area R_(r) is an area extending over a predetermined range on anouter side behind the crossing lane Ct in the traveling lane L1 of thehost vehicle a. In particular, when the stop position Pα is within therearward stop limit area R_(r), the rearward stop limit area R_(r) isset to a range in which a retracting departure of the preceding vehicleβ from the crossing lane Ct is considered to be blocked. In the presentembodiment, the rearward stop limit area R_(r) is stored in advance inthe storage area readable by the controller 20. Similar to the forwardstop limit area R_(f), an extension length of the rearward stop limitarea R_(r) may be appropriately adjusted according to the vehicle bodysize of the host vehicle a (in particular, vehicle length and vehiclewidth).

More specifically, the controller 20 determines whether the stopposition Pα is within the rearward stop limit area R_(r) by referring tothe surrounding image, the surrounding vehicle detection data, knownvehicle body size data of the host vehicle α, and/or the HD map. Then,when it is determined that the stop position Pα is within the rearwardstop limit area R_(r), the controller 20 executes second stop control instep S500.

In the second stop control in step S500, the controller 20 switches theat-stopping inter-vehicle distance Dβ to the second at-stoppinginter-vehicle distance Dβ₂ longer than the basic at-stoppinginter-vehicle distance Dβ₀.

Here, the second at-stopping inter-vehicle distance Dβ₂ is a correctionvalue that is set to increase and correct the basic at-stoppinginter-vehicle distance Dβ₀ from a viewpoint of changing the stopposition Pα rearward (direction in which the inter-vehicle distance tothe preceding vehicle β is increased) such that the stop position Pα isnot within the rearward stop limit area R_(r). The second at-stoppinginter-vehicle distance Dβ₂ is preferably set to a length that does notexcessively shorten the inter-vehicle distance between the host vehiclea and the following vehicle γ, while achieving an object of preventingthe stop position Pα from being within the rearward stop limit areaR_(r). Then, when the at-stopping inter-vehicle distance Dβ is switchedto the second at-stopping inter-vehicle distance Dβ₂, the controller 20executes the subsequent processing from step S700.

On the other hand, when it is determined in step S300 that the stopposition Pα is not within the rearward stop limit area R_(r), thecontroller 20 executes processing in step S600.

In basic stop control in step S600, the controller 20 maintains theat-stopping inter-vehicle distance Dβ at the basic at-stoppinginter-vehicle distance Dβ₀ (maintains the stop position Pα at the basicstop position Pα₀), and executes the subsequent processing from stepS700.

Next, when any one of the above-described first stop control (stepS400), second stop control (step S500), and basic stop control (stepS600) is ended, the controller 20 executes the processing in step S700.

In step S700, the controller 20 performs processing of displayinginformation to be notified to the occupant of the host vehicle a on thedisplay 6 in response to the execution of one of the first stop controland the second stop control. For example, when the first stop control isexecuted, the controller 20 displays, on the display 6, a textindicating that “because the rearward vehicle cannot depart, theinter-vehicle distance to the forward vehicle will be reduced” and imageinformation for assisting the occupant in understanding the text, asnecessary. On the other hand, when the second stop control is executed,the controller 20 displays, on the display 6, a text indicating that“because the forward vehicle cannot depart, an inter-vehicle distancewill be made” and image information for assisting the occupant inunderstanding the text, as necessary. The specific content displayed onthe display 6 is not limited thereto, and may be appropriately changed.

Then, in step S800, the controller 20 operates the actuator 5 such thatan actual inter-vehicle distance between the preceding vehicle β and thehost vehicle a approaches a distance determined by the first stopcontrol, the second stop control, or the basic stop control (that is,one of the first at-stopping inter-vehicle distance Dβ₁, the secondat-stopping inter-vehicle distance Dβ₂, and the basic at-stoppinginter-vehicle distance Dβ₀).

Therefore, when the first stop control (step S400) is executed, thecontroller 20 moves the host vehicle a such that the stop position Pα ofthe host vehicle a is changed from the basic stop position Pα₀ to aforward position (hereinafter also referred to as a “first correctedstop position Pα₁”). When the second stop control (step S500) isexecuted, the controller 20 moves the host vehicle a such that the stopposition Pα of the host vehicle a is changed from the basic stopposition Pα₀ to a rearward position (hereinafter also referred to as a“second corrected stop position Pα₂”). On the other hand, when the basicstop control (step S600) is executed, the controller 20 maintains thestop position Pα at the basic stop position Pα₀.

Next, an example of a control result when the autonomous driving controlmethod according to the present embodiment described above is applied toa specific scene will be described.

FIG. 3 is a diagram illustrating an example of a specific scene to whichthe first stop control is applied. In particular, in FIG. 3 , a scene inwhich the basic stop position Pα₀ of the host vehicle a is within theforward stop limit area R_(f) is assumed (see the host vehicle aindicated by a single-dot two-chain line). In this scene, when theautonomous driving control method according to the present embodiment isapplied, the at-stopping inter-vehicle distance Dβ is set to the firstat-stopping inter-vehicle distance Dβ₁ shorter than the basicat-stopping inter-vehicle distance Dβ₀ in accordance with control logicin step S200 and step S400. Therefore, since the host vehicle a movessuch that the stop position Pα is changed from the basic stop positionPα₀ to the first corrected stop position Pα₁ forward, a space betweenthe host vehicle a (more specifically, the rear end of the vehicle bodyof the host vehicle a) and the crossing lane Ct can be widened so as toallow advancing of the following vehicle γ.

On the other hand, FIG. 4 is a diagram illustrating an example of aspecific scene to which the second stop control is applied. Inparticular, in FIG. 4 , a scene in which the basic stop position Pα₀ ofthe host vehicle a is within the rearward stop limit area R_(r) isassumed (see the host vehicle a indicated by a single-dot two-chainline). In this scene, when the autonomous driving control methodaccording to the present embodiment is applied, the at-stoppinginter-vehicle distance Dβ is set to the second at-stopping inter-vehicledistance Dβ₂ longer than the basic at-stopping inter-vehicle distanceDβ₀ in accordance with control logic in step S200 and step S500.Therefore, since the host vehicle a moves such that the stop position Pαis changed from the basic stop position Pα₀ to the second corrected stopposition Pα₂ rearward, a space between the crossing lane Ct and the hostvehicle a (more specifically, a front end of the vehicle body of thehost vehicle a) can be widened so as to allow retracting of thepreceding vehicle β.

According to the present embodiment having the configuration describedabove, the following operations and effects are exerted.

In the present embodiment, an autonomous driving control method isprovided in which the host vehicle a is stopped such that theinter-vehicle distance to the preceding vehicle β is the predeterminedat-stopping inter-vehicle distance Dβ.

In the autonomous driving control method, when the stop position Pα ofthe host vehicle a is within the forward stop limit area R_(f) set infront of the crossing lane Ct (Yes in step S200), the first stop control(step S400) of setting the at-stopping inter-vehicle distance Dβ to thefirst at-stopping inter-vehicle distance Dβ₁ shorter than thepredetermined basic at-stopping inter-vehicle distance Dβ₀ is executed.In addition, when the stop position Pα of the host vehicle a is withinthe rearward stop limit area R_(r) set behind the crossing lane Ct (Yesin step S300), the second stop control (step S600) of setting theat-stopping inter-vehicle distance Dβ to the second at-stoppinginter-vehicle distance Dβ₂ longer than the basic at-stoppinginter-vehicle distance Dβ₀ is executed.

Accordingly, when the stop position Pα of the host vehicle a (inparticular, basic stop position Pα₀ is within the forward stop limitarea R_(f), the host vehicle a can be changed to a position in front ofthe original stop position Pα (first corrected stop position Pα₁).Therefore, a space between the host vehicle a in the stop state and thecrossing lane Ct located behind the host vehicle a can be widened. Thatis, since a space in which the following vehicle γ advances and retreatsfrom the crossing lane Ct can be secured, the following vehicle γ can beprevented from being left in the crossing lane Ct.

On the other hand, when the basic stop position Pα₀ is within therearward stop limit area R_(r), the host vehicle α can be changed to aposition behind the original stop position Pα (second corrected stopposition Pα₂). Therefore, a space between the host vehicle a in the stopstate and the crossing lane Ct located in front of the host vehicle acan be widened. That is, since a space in which the preceding vehicle βretracts and retreats from the crossing lane Ct can be secured, thepreceding vehicle β can be prevented from being left in the crossinglane Ct.

In addition, in this way, by preventing the preceding vehicle β or thefollowing vehicle γ from being left in the crossing lane Ct, travelingof a vehicle in the crossing lane Ct (for example, a vehicle in thecrossing traveling lane L2) can be suppressed from being blocked, andtraffic efficiency can be improved.

In particular, in the present embodiment, when the stop position Pα ofthe host vehicle a is within the forward stop limit area R_(f), theforward stop limit area R_(f) is set to a range in which the hostvehicle a blocks the advancing departure of the following vehicle γ fromthe crossing lane Ct. In addition, when the stop position Pα of the hostvehicle a is within the rearward stop limit area R_(r), the rearwardstop limit area R_(r) is set to a range in which the retractingdeparture of the preceding vehicle β from the crossing lane Ct isblocked.

Accordingly, specific control logic for accurately detecting a scene inwhich the host vehicle a stops in a state where the host vehicle a canblock the retreating of the following vehicle γ or the preceding vehicleβ from the crossing lane Ct, and appropriately changing the stopposition Pα of the host vehicle a in the scene is achieved.

Further, in the autonomous driving control method according to thepresent embodiment, the at-stopping inter-vehicle distance Dβ is set tothe basic at-stopping inter-vehicle distance Dβ₀ and the host vehicle ais stopped (step S101). Then, whether the stop position Pα of the hostvehicle a is within the forward stop limit area R_(f) or within therearward stop limit area R_(r), or within neither the forward stop limitarea R_(f) nor the rearward stop limit area R_(r) is determined (stepS200 and step S300). Then, when it is determined that the stop positionPα of the host vehicle a is within the forward stop limit area R_(f),the first stop control is executed (Yes in step S200, and step S400).When it is determined that the stop position Pα of the host vehicle a isnot within the rearward stop limit area R_(r), the second stop controlis executed (Yes in step S300, and step S500). When it is determinedthat the stop position Pα of the host vehicle a is within neither theforward stop limit area R_(f) nor the rearward stop limit area R_(r),the basic stop control of maintaining the basic at-stoppinginter-vehicle distance Dβ₀ is executed (No in step S200, No in stepS300, and step S600).

Accordingly, even after the host vehicle a is once stopped at the basicstop position Pa₀, specific control logic for changing the stop positionPα in a scene in which the host vehicle a can block the retreating ofthe following vehicle γ or the preceding vehicle β from the crossinglane Ct, and otherwise, maintaining the stop position Pα of the hostvehicle a at the original basic stop position Pa₀ is achieved.

According to the present embodiment, the controller 20 as an autonomousdriving control device for executing the above autonomous drivingcontrol method, that is, an autonomous driving control device that stopsthe host vehicle a such that the inter-vehicle distance to the precedingvehicle β is the predetermined at-stopping inter-vehicle distance Dβ isprovided.

The controller 20 includes at least one of a first stop control unit(step S400) and a second stop control unit (step S500). When the stopposition Pα of the host vehicle a is within the forward stop limit areaR_(f) set in front of the crossing lane Ct (Yes in step S200), the firststop control unit sets the at-stopping inter-vehicle distance Dβ to thefirst at-stopping inter-vehicle distance Dβ₁ shorter than thepredetermined basic at-stopping inter-vehicle distance Dβ₀. In addition,when the stop position Pα of the host vehicle a is within the rearwardstop limit area R_(r) set behind the crossing lane Ct (Yes in stepS300), the second stop control unit sets the at-stopping inter-vehicledistance Dβ to the second at-stopping inter-vehicle distance Dβ₂ longerthan the basic at-stopping inter-vehicle distance Dβ₀.

Accordingly, a suitable system configuration for executing the aboveautonomous driving control method is achieved.

Second Embodiment

Hereinafter, an autonomous driving control method according to a secondembodiment will be described. The same elements as those in the firstembodiment are denoted by the same reference numerals, and thedescription thereof will be omitted. In the present embodiment, anexample in which the stop position Pα of the host vehicle a is predictedin advance, and the stop position Pα is adjusted based on adetermination result of whether the predicted stop position Pα(hereinafter also referred to as a “scheduled stop position P^α”) iswithin the forward stop limit area R_(f) or the rearward stop limit areaR_(r) will be described.

FIG. 5 is a flowchart illustrating the autonomous driving control methodaccording to the present embodiment. The controller 20 repeatedlyexecutes processing described below at each predetermined controlperiod.

First, in step S100, the controller 20 acquires various types of inputinformation as in the first embodiment.

Next, in step S110, the controller 20 determines whether the hostvehicle a is scheduled to stop. Specifically, the controller 20 refersto a surrounding image and/or surrounding vehicle detection data and thelike, and determines whether the host vehicle a is in the process ofstopping (just before stop) with reference to whether the precedingvehicle speed Vβ related to the preceding vehicle β that is a followingtarget is equal to or less than a predetermined value.

In step S115, the controller 20 calculates the scheduled stop positionP^α. Specifically, on the premise that the at-stopping inter-vehicledistance Dβ is set to the basic at-stopping inter-vehicle distance Dβ₀,the controller 20 obtains, as the scheduled stop position P^α, aposition at which the host vehicle a is predicted to stop when the hostvehicle speed Va, the preceding vehicle speed Vβ, and a vehicle speeddifference ΔVαβ all reach zero. In the following description, thescheduled stop position P^α when the at-stopping inter-vehicle distanceDβ is set to the basic at-stopping inter-vehicle distance Dβ₀ isparticularly referred to as a “basic scheduled stop position P^α₀”.

Next, in step S120, the controller 20 determines whether the crossinglane Ct is present around the basic scheduled stop position P^α₀.Specifically, the controller 20 determines whether the crossing lane Ctis present around the basic scheduled stop position P^α₀ based on thesurrounding image, traveling route information, an HD map,vehicle-to-vehicle communication information, and/or road-to-vehiclecommunication information.

Then, when it is determined that the crossing lane Ct is not presentaround the basic scheduled stop position P^α₀, the controller 20executes basic stop control in step S600. That is, in this case, thecontroller 20 maintains the state where the at-stopping inter-vehicledistance Dβ is set to the basic at-stopping inter-vehicle distance Dβ₀.On the other hand, when it is determined that the crossing lane Ct ispresent around the basic scheduled stop position P^α₀, the controller 20executes subsequent processing from step S200′.

In step S200′, the controller 20 determines whether the basic scheduledstop position P^α₀ is within the forward stop limit area R_(f) of thecrossing lane Ct. Specifically, the controller 20 executes thedetermination by referring to the surrounding image, the traveling routeinformation, and/or the HD map based on whether coordinates of the basicscheduled stop position P^α₀ in a predetermined coordinate system (forexample, world coordinates) are within a range that defines the forwardstop limit area R_(f) on the same coordinate system.

Then, when it is determined that the basic scheduled stop position P^α₀is within the forward stop limit area R_(f), the controller 20 executesfirst stop control in step S400. That is, similar to the firstembodiment, the controller 20 switches the at-stopping inter-vehicledistance Dβ from the basic at-stopping inter-vehicle distance Dβ₀ to thefirst at-stopping inter-vehicle distance Dβ₁ shorter than the basicat-stopping inter-vehicle distance Dβ₀.On the other hand, when it isdetermined that the basic scheduled stop position P^α₀ is not within theforward stop limit area R_(f), the controller 20 executes processing instep S300′.

In step S300′, the controller 20 determines whether the basic scheduledstop position P^α₀ is within the rearward stop limit area R_(r) of thecrossing lane Ct. Specifically, the controller 20 executes thedetermination by referring to the surrounding image, the traveling routeinformation, and/or the HD map based on whether coordinates of the basicscheduled stop position P^α₀ in a predetermined coordinate system (forexample, world coordinates) are within a range that defines the rearwardstop limit area R_(r) on the same coordinate system.

Then, when it is determined that the basic scheduled stop position P^α₀is within the rearward stop limit area R_(r), the controller 20 executessecond stop control in step S500. That is, similar to the firstembodiment, the controller 20 switches the at-stopping inter-vehicledistance Dβ from the basic at-stopping inter-vehicle distance Dβ₀ to thesecond at-stopping inter-vehicle distance Dβ₂ longer than the basicat-stopping inter-vehicle distance Dβ₀. On the other hand, when it isdetermined that the basic scheduled stop position P^α₀ is not within therearward stop limit area R_(r), the controller 20 executes processing instep S600 (basic stop control). That is, the controller 20 maintains thescheduled stop position P^α of the host vehicle a at the basic scheduledstop position P^α₀.

According to the autonomous driving control method of the presentembodiment having the configuration described above, the followingoperations and effects are exerted.

In the autonomous driving control method according to the presentembodiment, the at-stopping inter-vehicle distance Dβ is set to thebasic at-stopping inter-vehicle distance Dβ₀ and the stop position Pα(scheduled stop position P^α) when the host vehicle a is stopped (stepS115) is predicted. In addition, whether the predicted scheduled stopposition P^α (in particular, basic scheduled stop position P^α₀) iswithin the forward stop limit area R_(f) or the rearward stop limit areaR_(r) is determined (step S200′ and step S300′). Then, when it isdetermined that the basic scheduled stop position P^α₀ is within theforward stop limit area R_(f), the first stop control is executed (Yesin step S200′, and step S400). On the other hand, when it is determinedthat the basic scheduled stop position P^α₀ is within the rearward stoplimit area R_(r), the second stop control is executed (Yes in stepS300′, and step S500). When it is determined that the basic scheduledstop position P^α₀ is within neither the forward stop limit area R_(f)nor the rearward stop limit area R_(r), the basic stop control ofmaintaining the basic at-stopping inter-vehicle distance Dβ₀ is executed(No in step S200′, No in step S300′, and step S600).

Accordingly, when the host vehicle a is traveling, specific controllogic for predicting a situation in which the stop position Pα when thevehicle is actually stopped is within the forward stop limit area R_(f)or the rearward stop limit area R_(r) (that is, a situation in which theretreating of the following vehicle γ or the preceding vehicle β fromthe crossing lane Ct is blocked) in advance, and appropriately adjustingthe at-stopping inter-vehicle distance Dβ is achieved. Therefore, sincethe host vehicle a can be directly stopped so as not to block theretreating of the following vehicle γ or the preceding vehicle β fromthe crossing lane Ct, control of moving the host vehicle a again aftertemporary stop can be omitted. As a result, the situation in which thefollowing vehicle γ or the preceding vehicle β is left in the crossinglane Ct can be prevented, and discomfort of an occupant caused by movingthe host vehicle a again after the stop can be reduced.

Third Embodiment

Hereinafter, a third embodiment will be described. The same elements asthose in the first embodiment or the second embodiment are denoted bythe same reference numerals, and the description thereof will beomitted. In the present embodiment, a control mode in which, based onthe autonomous driving control method described with reference to FIG. 5, whether the following vehicle γ is present in the crossing lane Ct isdetermined, and the at-stopping inter-vehicle distance Dβ is setaccording to the determination result will be described.

FIG. 6 is a flowchart illustrating an autonomous driving control methodaccording to the present embodiment. For simplification of the drawings,blocks of step S100, step S115, and step S120, which are common to thosein FIG. 5 , are not illustrated.

In particular, in the present embodiment, when it is determined in stepS200′ that the basic scheduled stop position P^α₀ is within the forwardstop limit area R_(f) of the crossing lane Ct, the controller 20executes processing in step S210.

In step S210, the controller 20 determines whether the following vehicleγ is present in the crossing lane Ct. Specifically, the controller 20determines whether the following vehicle γ is present in the crossinglane Ct by referring to a surrounding image (in particular, an imageobtained by imaging a rearward of the host vehicle a), surroundingvehicle detection data, and/or vehicle-to-vehicle communicationinformation.

Then, when it is determined that the following vehicle γ is present inthe crossing lane Ct, the controller 20 executes first stop control instep S400. On the other hand, when it is determined that the followingvehicle γ is not present in the crossing lane Ct, the controller 20executes processing in step S600 (basic stop control). That is, thecontroller 20 maintains the at-stopping inter-vehicle distance Dβ at thebasic at-stopping inter-vehicle distance Dβ₀.

On the other hand, when it is determined in step S200′ that the basicscheduled stop position P^α₀ is not within the forward stop limit areaR_(f) and it is determined in subsequent step S300′ that the basicscheduled stop position P^α₀ is within the rearward stop limit areaR_(r), the controller 20 executes processing in step S310.

In step S310, the controller 20 determines whether the preceding vehicleβ is present in the crossing lane Ct. Specifically, the controller 20determines whether the preceding vehicle β is present in the crossinglane Ct by referring to a surrounding image (in particular, an imageobtained by imaging a frontward of the host vehicle a), the surroundingvehicle detection data, and/or the vehicle-to-vehicle communicationinformation.

Then, when it is determined that the preceding vehicle β is present inthe crossing lane Ct, the controller 20 executes second stop control instep S500. On the other hand, when it is determined that the precedingvehicle β is not present in the crossing lane Ct, the controller 20executes the basic stop control in step S600.

According to the autonomous driving control method of the presentembodiment having the configuration described above, the followingoperations and effects are exerted.

In the autonomous driving control method according to the presentembodiment, when the stop position Pα (basic scheduled stop positionP^α₀) of the host vehicle a is within the forward stop limit area R_(f),whether the following vehicle γ is present in the crossing lane Ct isfurther determined (Yes in step S200′, and step S210). Then, when it isdetermined that the following vehicle γ is present, the first stopcontrol is executed (Yes in step S210, and step S400), and when it isdetermined that the following vehicle γ is not present, the at-stoppinginter-vehicle distance Dβ is maintained at the basic at-stoppinginter-vehicle distance Dβ₀ (No in step S210, and step S600).

When the basic scheduled stop position P^α₀ of the host vehicle a iswithin the rearward stop limit area R_(r), whether the preceding vehicleβ is present in the crossing lane Ct is further determined (Yes in stepS300′, and step S310). Then, when it is determined that the precedingvehicle β is present, the second stop control is executed (Yes in stepS310, and step S500), and when it is determined that the precedingvehicle β is not present, the at-stopping inter-vehicle distance Dβ ismaintained at the basic at-stopping inter-vehicle distance Dβ₀ (No instep S310, and step S600).

Accordingly, specific control logic for adjusting the at-stoppinginter-vehicle distance Dβ after confirming the presence or absence ofthe following vehicle γ or the preceding vehicle β that may be left inthe crossing lane Ct in a scene in which the stop position Pα of thehost vehicle α is within the forward stop limit area R_(f) or therearward stop limit area R_(r) is achieved. Therefore, the control ofchanging the stop position Pα of the host vehicle a from the basic stopposition Pα₀ to the first corrected stop position Pα₁ forward or thesecond corrected stop position Pα₂ rearward can be limited and executedin a scene in which the following vehicle γ or the preceding vehicle βis likely to be left in the crossing lane Ct. As a result, specificcontrol logic that can suppress a situation in which the stop positionPα of the host vehicle a is unnecessarily changed from the originallydesired basic stop position Pα₀ is achieved.

Fourth Embodiment

Hereinafter, a fourth embodiment will be described. The same elements asthose in the first to third embodiments are denoted by the samereference numerals, and the description thereof will be omitted. In thepresent embodiment, a mode related to specific processing in first stopcontrol (step S400) will be described. In particular, in the first stopcontrol according to the present embodiment, instead of immediatelyswitching the at-stopping inter-vehicle distance Dβ from the basicat-stopping inter-vehicle distance Dβ₀ to the first at-stoppinginter-vehicle distance Dβ₁, the switching is executed when a certaincondition is satisfied.

FIG. 7 is a flowchart illustrating the first stop control according tothe present embodiment.

As illustrated, first, in step S410, the controller 20 determineswhether the following vehicle γ is present in a predetermined distancerange in front of the crossing lane Ct. The distance range is set to anappropriate range from a viewpoint of determining whether the followingvehicle γ is approaching the crossing lane Ct to such an extent that thefollowing vehicle γ is blocked by the host vehicle a in the stop stateand is left in the crossing lane Ct.

Specifically, the controller 20 determines whether the following vehicleγ is present in the above distance range by referring to a surroundingimage (in particular, an image obtained by imaging a rearward of thehost vehicle a), surrounding vehicle detection data, and/orvehicle-to-vehicle communication information.

Then, when it is determined that the following vehicle γ is not presentin the distance range (more specifically, when it is determined that thefollowing vehicle γ is present in the crossing lane Ct), the controller20 proceeds the processing to step S450, and switches the at-stoppinginter-vehicle distance Dβ from the basic at-stopping inter-vehicledistance Dβ₀ to the first at-stopping inter-vehicle distance Dβ₁. On theother hand, when it is determined that the following vehicle γ ispresent in the distance range, the controller 20 executes processing instep S420.

In step S420, the controller 20 refers to an image from the in-vehiclecamera 1 a and/or surrounding vehicle detection data, and obtains aseparation distance Dα_(Ct) from the host vehicle a to the crossing laneCt rearward (see FIG. 3 ).

Next, in step S430, the controller 20 determines whether the separationdistance Dα_(Ct) is equal to or less than a predetermined distancethreshold D_(th). The distance threshold D_(th) is set to an appropriatevalue as a reference for determining whether a magnitude of theseparation distance Dα_(Ct) allows the following vehicle γ to enter aspace between the host vehicle a and the crossing lane Ct.

Then, when it is determined that the separation distance Dα_(Ct) isequal to or less than the distance threshold D_(th), the controller 20proceeds the processing to step S440, and maintains the at-stoppinginter-vehicle distance Dβ at the basic at-stopping inter-vehicledistance Dβ₀. On the other hand, when it is determined that theseparation distance Dα_(Ct) is not equal to or less than the distancethreshold D_(th) (when it is determined that the separation distanceDα_(Ct) exceeds the distance threshold D_(th)), the controller 20proceeds he processing to step S450, and switches the at-stoppinginter-vehicle distance Dβ from the basic at-stopping inter-vehicledistance Dβ₀ to the first at-stopping inter-vehicle distance Dβ₁.

According to the autonomous driving control method of the presentembodiment having the configuration described above, the followingoperations and effects are exerted.

In the first stop control in the autonomous driving control methodaccording to the present embodiment, whether the following vehicle γ ispresent in the predetermined distance range in front of the crossinglane Ct is determined (step S410). Then, when it is determined that thefollowing vehicle γ is present in the distance range, whether theseparation distance Dα_(Ct) from the host vehicle a to the crossing laneCt rearward exceeds the predetermined distance threshold D_(th) isdetermined (step S420 and step S430). Then, when it is determined thatthe separation distance Dα_(Ct) exceeds the distance threshold D_(th),the at-stopping inter-vehicle distance Dβ is switched from the basicat-stopping inter-vehicle distance Dβ₀ to the first at-stoppinginter-vehicle distance Dβ₁ (No in step S430, and step S450). Inaddition, when it is determined that the separation distance Dα_(Ct)does not exceed the distance threshold D_(th), the at-stoppinginter-vehicle distance Dβ is maintained at the basic at-stoppinginter-vehicle distance Dβ₀ (Yes in step S430, and step S440).

Accordingly, when the space between the host vehicle a and the crossinglane Ct is not sufficiently wide from the viewpoint of allowing thefollowing vehicle γ to enter (separation distance Dα_(Ct) ≤ distancethreshold D_(th)), the stop position Pα of the host vehicle a ismaintained at the basic stop position Pα₀. Therefore, even though thespace between the host vehicle a and the crossing lane Ct is notsufficiently wide, the following vehicle γ can be prevented from beingforced to enter the above space, which is slightly widened as a resultof the host vehicle a stopping at the first corrected stop position Pα₁in front of the basic stop position Pα₀. In addition, when the spacebetween the host vehicle a and the crossing lane Ct is sufficiently widefrom the viewpoint of allowing the following vehicle γ to enter(separation distance Dα_(Ct) > distance threshold D_(th)), theat-stopping inter-vehicle distance Dβ is switched to the firstat-stopping inter-vehicle distance Dβ₁. Accordingly, even when the hostvehicle a is stopped at the basic stop position Pα₀, the above space isfurther widened in a relatively wide state, and thus the followingvehicle γ can be encouraged to enter the space. As a result, trafficefficiency can be improved by promoting the following vehicle γ to crossthe crossing lane Ct.

Fifth Embodiment

Hereinafter, a fifth embodiment will be described. The same elements asthose in the first to fourth embodiments are denoted by the samereference numerals, and the description thereof will be omitted. In thepresent embodiment, a control mode in which, based on the autonomousdriving control method according to the second embodiment described withreference to FIG. 5 , switching of a priority related to passage in thecrossing lane Ct is further determined, and the at-stoppinginter-vehicle distance Dβ is set according to a determination resultwill be described.

FIG. 8 is a flowchart illustrating an autonomous driving control methodaccording to the present embodiment. For simplification of the drawings,blocks of step S100, step S115, and step S120, which are common to thosein FIG. 5 , are not illustrated.

In particular, in the present embodiment, in step S121, the controller20 executes priority switching processing of predicting switching of apriority in traveling in the crossing lane Ct. Specifically, thecontroller 20 predicts whether a traveling priority of the precedingvehicle β, the host vehicle α, and the following vehicle γ in thetraveling lane L1 is switched to the crossing traveling lane L2 (inparticular, whether the traveling priority in the traveling lane L1 islost) by using a surrounding image, vehicle-to-vehicle communicationinformation, and/or road-to-vehicle communication information as inputinformation.

More specifically, the controller 20 calculates a prediction time untilsignal display in the traveling lane L1 of the host vehicle α isswitched from a traffic permission display (green light) to a trafficprohibition display (red light) (hereinafter also referred to as a“priority switching prediction time”).

FIG. 9 is a diagram illustrating an example of a specific scene in whichexecution of the priority switching processing is assumed. Asillustrated, the controller 20 obtains, from the input information, eachdisplay (for example, turn-on or turn-off states of red, yellow, andgreen light) of a vehicle traffic light sv 1 for displaying travelingpermission or non-permission in the traveling lane L1 of the hostvehicle α, a vehicle traffic light sv 2 for displaying travelingpermission or non-permission in the crossing traveling lane L2, apedestrian traffic light sp 1 for displaying traveling permission ornon-permission in a crosswalk along the traveling lane L1, and apedestrian traffic light sp 2 for displaying traveling permission ornon-permission in a crosswalk along the crossing traveling lane L2,and/or a switching pattern of these displays to calculate the priorityswitching prediction time.

Next, in step S122, the controller 20 determines whether the priority isswitched. Specifically, the controller 20 determines that the priorityis switched when the priority switching prediction time calculated instep S122 is equal to or less than a predetermined time threshold, anddetermines that the priority is not switched when the priority switchingprediction time exceeds the time threshold. The time threshold is setto, when the basic scheduled stop position P^α₀ of the host vehicle α iswithin the forward stop limit area Rf or the rearward stop limit areaR_(r), an appropriate time from a viewpoint of determining whether atiming at which the traveling priority in the traveling lane L1 in thetraveling lane L1 (that is, the traveling lane L1 of the precedingvehicle β and the following vehicle γ) is lost is approaching to theextent that an actual possibility that the preceding vehicle β or thefollowing vehicle γ is left in the crossing lane Ct is assumed.

Then, when it is determined that the priority is switched, thecontroller 20 executes subsequent processing from step S200′ in the samemanner as in the second embodiment, and switches the at-stoppinginter-vehicle distance Dβ to the first at-stopping inter-vehicledistance Dβ₁ or the second at-stopping inter-vehicle distance Dβ₂. Onthe other hand, when it is determined that the priority is not switched,the controller 20 executes basic stop control. That is, in this case, itis determined that the preceding vehicle β or the following vehicle γ isnot left in the crossing lane Ct, and the at-stopping inter-vehicledistance Dβ is maintained at the basic at-stopping inter-vehicledistance Dβ₀.

According to the autonomous driving control method of the presentembodiment having the configuration described above, the followingoperations and effects are exerted.

In the autonomous driving control method according to the presentembodiment, whether the detected priority in the crossing lane Ct isswitched is determined (step S122), and when it is determined that thepriority is not switched, the at-stopping inter-vehicle distance Dβ ismaintained at the basic at-stopping inter-vehicle distance Dβ₀ (No instep S122, and step S600).

Accordingly, control of changing the stop position Pα of the hostvehicle α to the first corrected stop position Pα₁ in front of the basicstop position Pα₀ or the second corrected stop position Pα₂ behind thebasic stop position Pα₀ can be limited and executed in a situation inwhich the following vehicle γ or the preceding vehicle β is left in thecrossing lane Ct (situation in which the traveling priority in thetraveling lane L1 is lost within the priority switching predictiontime). Therefore, specific control logic that can suppress a situationin which the stop position Pα of the host vehicle α is unnecessarilychanged from the originally desired basic stop position Pα₀ is achieved.

A configuration may be adopted in which the priority switchingprediction time is calculated by referring to a behavior of othervehicles and/or pedestrians present inside or around the crossing laneCt (such as a start timing of the vehicle and a crossing start timing ofthe pedestrian) instead of or in addition to each display (for example,turn-on or turn-off states of red, yellow, and green light) of thevehicle traffic light sv 1, the vehicle traffic light sv 2, thepedestrian traffic light sp 1, and/or the pedestrian traffic light sp 2in the present embodiment.

Sixth Embodiment

Hereinafter, a sixth embodiment will be described. The same elements asthose in the first to fifth embodiments are denoted by the samereference numerals, and the description thereof will be omitted.

In the present embodiment, the controller 20 determines a magnitude ofthe first at-stopping inter-vehicle distance Dβ₁, a magnitude of thesecond at-stopping inter-vehicle distance Dβ₂, or both based on thenumber of vehicles present in the crossing lane Ct.

More specifically, during first stop control, the controller 20calculates the number of vehicles present in the crossing lane Ct basedon a surrounding image, vehicle-to-vehicle communication information,and/or road-to-vehicle communication information. In the presentembodiment, the vehicles in the crossing lane Ct to be detected includeother vehicles other than the preceding vehicle β or the followingvehicle γ (other vehicles further preceding the preceding vehicle β orother vehicles further following the following vehicle γ). Then, thecontroller 20 determines the first at-stopping inter-vehicle distanceDβ₁ according to the number of vehicles calculated by referring to apredetermined map. Similarly, the controller 20 determines the secondat-stopping inter-vehicle distance Dβ₂ according to the number ofvehicles present in the crossing lane Ct during second stop control.

FIG. 10 is a diagram illustrating an example of a map for defining arelationship between the number of vehicles present in the crossing laneCt and the first at-stopping inter-vehicle distance Dβ₁ (secondat-stopping inter-vehicle distance Dβ₂) to be set. As illustrated, inthe present embodiment, the first at-stopping inter-vehicle distance Dβ₁(second at-stopping inter-vehicle distance Dβ₂) is set to be longer thanthe basic at-stopping inter-vehicle distance Dβ₀ as the number ofvehicles present in the crossing lane Ct increases.

As described above, in the present embodiment, at least one of the firstat-stopping inter-vehicle distance Dβ₁ and the second at-stoppinginter-vehicle distance Dβ₂ is determined based on the number of vehiclespresent in the crossing lane Ct.

Accordingly, an amount of changing the stop position Pα of the hostvehicle α from the basic stop position Pα₀ can be determined accordingto the number of other vehicles that may be actually left in thecrossing lane Ct. Accordingly, a deviation width of the actual stopposition Pα with respect to the basic stop position Pα₀ which isoriginally intended can be appropriately reduced depending on thesituation while preventing the preceding vehicle β or the followingvehicle γ from being left in the crossing lane Ct.

FIG. 10 illustrates an example in which the magnitudes of the firstat-stopping inter-vehicle distance Dβ₁and the second at-stoppinginter-vehicle distance Dβ₂ when the number of vehicles present in thecrossing lane Ct is the same are set to be the same. However, thepresent invention is not limited thereto, and a mode in which themagnitudes of the first at-stopping inter-vehicle distance Dβ₁ and thesecond at-stopping inter-vehicle distance Dβ₂ with respect to the numberof vehicles present in the crossing lane Ct differ from each other maybe adopted depending on the situation.

Seventh Embodiment

Hereinafter, a seventh embodiment will be described. The same elementsas those in the first to sixth embodiments are denoted by the samereference numerals, and the description thereof will be omitted. In thepresent embodiment, an example of control of defining a timing at whichthe at-stopping inter-vehicle distance Dβ is returned to the basicat-stopping inter-vehicle distance Dβ₀ when the at-stoppinginter-vehicle distance Dβ is set to the first at-stopping inter-vehicledistance Dβ₁ or the second at-stopping inter-vehicle distance Dβ₂ andthe host vehicle α is stopped will be described.

FIG. 11 is a flowchart illustrating an autonomous driving control methodaccording to the present embodiment. For simplification of the drawings,blocks up to step S800, which are common to those in FIGS. 2, 5, 6, or 8, are not illustrated. That is, each processing illustrated in FIG. 11is started after the processing in step S800.

First, in step S900, the controller 20 determines whether the hostvehicle α is stopped based on the host vehicle speed Vα or the like.Then, when it is determined that the host vehicle α is not stopped, thecontroller 20 ends this routine, and when it is determined that the hostvehicle α is stopped, the controller 20 executes determination in stepS1000 and step S1010.

In steps S1000 and S1010, the controller 20 determines whether theat-stopping inter-vehicle distance Dβ is set to the first at-stoppinginter-vehicle distance Dβ₁ or the second at-stopping inter-vehicledistance Dβ₂. Then, when it is determined that the at-stoppinginter-vehicle distance Dβ is set to neither the first at-stoppinginter-vehicle distance Dβ₁ nor the second at-stopping inter-vehicledistance Dβ₂ (that is, is set to the basic at-stopping inter-vehicledistance Dβ₀), the controller 20 ends this routine. On the other hand,when it is determined that the at-stopping inter-vehicle distance Dβ isset to the first at-stopping inter-vehicle distance Dβ₁ or the secondat-stopping inter-vehicle distance Dβ₂, the controller 20 executesprocessing in step S1100.

In step S1100, the controller 20 determines whether a vehicle is presentin the crossing lane Ct by referring to a surrounding image, surroundingvehicle detection data, and/or vehicle-to-vehicle communicationinformation. In the present embodiment, the vehicles in the crossinglane Ct to be detected include other vehicles other than the precedingvehicle β or the following vehicle γ (other vehicles further precedingthe preceding vehicle β or other vehicles further following thefollowing vehicle γ).

Then, when it is determined that a vehicle is present in the crossinglane Ct, the controller 20 maintains the at-stopping inter-vehicledistance Dβ at the first at-stopping inter-vehicle distance Dβ₁ or thesecond at-stopping inter-vehicle distance Dβ₂ in step S1200. On theother hand, when it is determined that no vehicle is present in thecrossing lane Ct, the controller 20 switches the at-stoppinginter-vehicle distance Dβ from the first at-stopping inter-vehicledistance Dβ₁ or the second at-stopping inter-vehicle distance Dβ₂ to thebasic at-stopping inter-vehicle distance Dβ₀.

As described above, in the present embodiment, after the host vehicle αis stopped based on the first at-stopping inter-vehicle distance Dβ₁ orthe second at-stopping inter-vehicle distance Dβ₂ (Yes in step S900), astate where the at-stopping inter-vehicle distance Dβ is set to thefirst at-stopping inter-vehicle distance Dβ₁ or the second at-stoppinginter-vehicle distance Dβ₂ is maintained until it is determined that novehicle is present in the crossing lane Ct (step S1100 to step S1300).

Accordingly, when the stop position Pα of the host vehicle α is thefirst corrected stop position Pα₁ or the second corrected stop positionPα₂ deviated from the basic stop position Pα₀, the stop position Pα ismaintained until no vehicle is present in the crossing lane Ct. That is,while the situation in which a vehicle that may be left in the crossinglane Ct is present continues, a state where a space for retracting thefollowing vehicle γ or the preceding vehicle β from the crossing lane Ctis formed can be maintained. Therefore, the following vehicle γ or thepreceding vehicle β can be more reliably prevented from being left inthe crossing lane Ct.

According to the autonomous driving control method of the presentembodiment, even when the preceding vehicle β moves while the hostvehicle α is stopped, the host vehicle α moves following the precedingvehicle β so as to maintain the first corrected stop position Pα₁ or thesecond corrected stop position Pα₂. That is, the host vehicle α followsthe preceding vehicle β so as to maintain a relatively shortinter-vehicle distance (first at-stopping inter-vehicle distance Dβ₁) ora relatively long inter-vehicle distance (second at-stoppinginter-vehicle distance Dβ₂) with respect to the preceding vehicle β.Therefore, an intention of the host vehicle α for making a space, forthe following vehicle γ or the preceding vehicle β to retreat from thecrossing lane Ct, for the preceding vehicle β or the following vehicle γcan be more reliably recognized. As a result, cooperation (retracting ofthe following vehicle γ or advancing of the preceding vehicle β) formaking the space by the preceding vehicle β or the following vehicle γcan be promoted, and the following vehicle γ or the preceding vehicle βcan be more reliably prevented from being left in the crossing lane Ct.

Modification 1

FIG. 12A is a diagram illustrating a modification of a scene to whichthe autonomous driving control method can be applied. In the aboveembodiments, the examples in which the autonomous driving controlmethods (in particular, first stop control) according to the embodimentsare applied in a scene in which both the host vehicle α and thefollowing vehicle γ are traveling straight in the same traveling lane L1(see FIG. 4 ) are described, but as illustrated in FIG. 12A, theautonomous driving control methods according to the embodiments may beapplied when the following vehicle γ turns right from the crossingtraveling lane L2 toward the traveling lane L1 in the crossing lane Ct.

Although not illustrated, the autonomous driving control method (inparticular, second stop control) according to the embodiments may beapplied when the preceding vehicle β turns right from the crossingtraveling lane L2 toward the traveling lane L1 in the crossing lane Ct.

Modification 2

FIG. 12B is a diagram illustrating a modification of a scene to whichthe autonomous driving control method can be applied. As illustrated,the autonomous driving control methods according to the embodiments maybe applied when the following vehicle γ turns left from the crossingtraveling lane L2 toward the traveling lane L1 in the crossing lane Ct.In addition, although not illustrated, the autonomous driving controlmethods according to the embodiments may be applied when the precedingvehicle β turns left in the crossing lane Ct.

Modification 3

FIG. 12C is a diagram illustrating a modification of a scene to whichthe autonomous driving control method can be applied. As illustrated,the autonomous driving control methods according to the embodiments maybe applied when the crossing lane Ct includes the traveling lane L1 ofthe host vehicle α, a sidewalk intersecting with the traveling lane L1,and traffic lights (vehicle traffic light sv 1 and pedestrian trafficlight sp 2) (when the crossing traveling lane L2 is not present).

Modification 4

FIG. 12D is a diagram illustrating a modification of a scene to whichthe autonomous driving control method can be applied. As illustrated,the autonomous driving control methods according to the embodiments maybe applied when the crossing lane Ct includes the traveling lane L1 ofthe host vehicle α, a line L3 intersecting with the traveling lane L1, arailroad crossing rc for determining permission or non-permission ofpassage in the traveling lane L1, and traffic lights (vehicle trafficlight sv 1 and railroad crossing traffic light st 3).

In particular, in the scene of the present modification, when theautonomous driving control method according to the fifth embodiment(FIG. 8 ) is applied, a configuration in which the priority switchingprediction time is calculated based on each display of the vehicletraffic light sv 1 and/or the railroad crossing traffic light st 3 maybe adopted. On the other hand, in the present modification, from aviewpoint of more reliably preventing the vehicle from being left in therailroad crossing rc, it is preferable to apply control logic thatexecutes processing from step S200 (that is, control logic describedwith reference to FIGS. 2 or 5 ) without executing processing (step S111and step S112) related to the priority switching determinationillustrated in FIG. 8 .

Although the embodiments of the present invention have been described,the above embodiments are merely a part of application examples of thepresent invention, and do not mean that the technical scope of thepresent invention is limited to the specific configurations of the aboveembodiments.

For example, in the above embodiments, an autonomous driving controlmethod that adopts both control in which the possibility that thefollowing vehicle γ is left in the crossing lane Ct is assumed (forexample, determination in step S200 and first stop control in step S400in FIG. 2 ) and control in which the possibility that the precedingvehicle β is left in the crossing lane Ct is assumed (for example,determination in step S300 and second stop control in step S500 in FIG.2 ) is described. However, an autonomous driving control method usingonly one of these control is also included in the technical scope of thepresent invention.

The above embodiments can be combined with each other in any combinationwithin a range in which contradiction does not occur. For example, thecontrol according to the third embodiment to the seventh embodiment isnot limited to the control based on the autonomous driving controlmethod according to the second embodiment, and may be performed based onthe autonomous driving control method according to the first embodiment.

An autonomous driving control program for causing the controller 20,which is a computer, to execute the autonomous driving control methodsdescribed in the above embodiments and a storage medium storing theautonomous driving control program are also included in the scope of thematters described in the description at the time of filing of thepresent application.

1. An autonomous driving control method for stopping a host vehicle suchthat an inter-vehicle distance to a preceding vehicle is a predeterminedat-stopping inter-vehicle distance, the method comprising: executing afirst stop control of setting an at-stopping inter-vehicle distance to afirst at-stopping inter-vehicle distance shorter than a predeterminedbasic at-stopping inter-vehicle distance when a stop position of thehost vehicle is within a forward stop limit area set in front of acrossing lane, and/or executing a second stop control of setting theat-stopping inter-vehicle distance to a second at-stopping inter-vehicledistance longer than the predetermined basic at-stopping inter-vehicledistance when the stop position of the host vehicle is within a rearwardstop limit area set behind the crossing lane.
 2. The autonomous drivingcontrol method according to claim 1, wherein when the stop position ofthe host vehicle is within the forward stop limit area, the forward stoplimit area is set to a range in which the host vehicle blocks anadvancing departure of a following vehicle from the crossing lane,and/or when the stop position of the host vehicle is within the rearwardstop limit area, the rearward stop limit area is set to a range in whichthe host vehicle blocks a retracting departure of the preceding vehiclefrom the crossing lane.
 3. The autonomous driving control methodaccording to claim 2, wherein the at-stopping inter-vehicle distance isset to the predetermined basic at-stopping inter-vehicle distance andthe host vehicle is stopped, whether the stop position of the hostvehicle is within the forward stop limit area or within the rearwardstop limit area, or within neither the forward stop limit area nor therearward stop limit area is determined, when it is determined that thestop position of the host vehicle is within the forward stop limit area,the first stop control is executed, when it is determined that the stopposition of the host vehicle is not within the rearward stop limit area,the second stop control is executed, and when it is determined that thestop position of the host vehicle is within neither the forward stoplimit area nor the rearward stop limit area, basic stop control ofmaintaining the predetermined basic at-stopping inter-vehicle distanceis executed.
 4. The autonomous driving control method according to claim2, wherein the at-stopping inter-vehicle distance is set to thepredetermined basic at-stopping inter-vehicle distance and a stopposition when the host vehicle is stopped is predicted, whether thepredicted stop position of the host vehicle is within the forward stoplimit area or the rearward stop limit area is determined, when it isdetermined that the stop position of the host vehicle is within theforward stop limit area, the first stop control is executed, when it isdetermined that the stop position of the host vehicle is within therearward stop limit area, the second stop control is executed, and whenit is determined that the stop position of the host vehicle is withinneither the forward stop limit area nor the rearward stop limit area,basic stop control of maintaining the predetermined basic at-stoppinginter-vehicle distance is executed.
 5. The autonomous driving controlmethod according to claim 2, wherein when the stop position of the hostvehicle is within the forward stop limit area, whether the followingvehicle is present in the crossing lane is further determined, when itis determined that the following vehicle is present, the first stopcontrol is executed, when it is determined that the following vehicle isnot present, the at-stopping inter-vehicle distance is maintained at thepredetermined basic at-stopping inter-vehicle distance, and/or when thestop position of the host vehicle is within the rearward stop limitarea, whether the preceding vehicle is present in the crossing lane isfurther determined, when it is determined that the preceding vehicle ispresent, the second stop control is executed, and when it is determinedthat the preceding vehicle is not present, the at-stopping inter-vehicledistance is maintained at the predetermined basic at-stoppinginter-vehicle distance.
 6. The autonomous driving control methodaccording to claim 2, wherein in the first stop control, whether thefollowing vehicle is present in a predetermined distance range in frontof the crossing lane is determined, whether a separation distance fromthe host vehicle to the crossing lane behind the host vehicle exceeds apredetermined distance threshold is determined, when it is determinedthat the separation distance exceeds the predetermined distancethreshold, the at-stopping inter-vehicle distance is switched from thepredetermined basic at-stopping inter-vehicle distance to the firstat-stopping inter-vehicle distance, and when it is determined that theseparation distance does not exceed the predetermined distancethreshold, the at-stopping inter-vehicle distance is maintained at thepredetermined basic at-stopping inter-vehicle distance.
 7. Theautonomous driving control method according to claim 1, wherein whethera detected priority in the crossing lane is switched is determined, andwhen it is determined that the detected priority is not switched, theat-stopping inter-vehicle distance is maintained at the predeterminedbasic at-stopping inter-vehicle distance.
 8. The autonomous drivingcontrol method according to claim 1, wherein at least one of the firstat-stopping inter-vehicle distance and the second at-stoppinginter-vehicle distance is determined based on a number of vehiclespresent in the crossing lane.
 9. The autonomous driving control methodaccording to claim 1, wherein after the host vehicle is stopped based onthe first at-stopping inter-vehicle distance or the second at-stoppinginter-vehicle distance, a state where the at-stopping inter-vehicledistance is set to the first at-stopping inter-vehicle distance or thesecond at-stopping inter-vehicle distance is maintained until it isdetermined that no vehicle is present in the crossing lane.
 10. Anautonomous driving control device for stopping a host vehicle such thatan inter-vehicle distance to a preceding vehicle is a predeterminedat-stopping inter-vehicle distance, the device comprising: at least oneof a first stop control unit and a second stop control unit, wherein thefirst stop control unit sets an at-stopping inter-vehicle distance to afirst at-stopping inter-vehicle distance shorter than a predeterminedbasic at-stopping inter-vehicle distance when a stop position of thehost vehicle is within a forward stop limit area set in front of acrossing lane, and the second stop control unit sets the at-stoppinginter-vehicle distance to a second at-stopping inter-vehicle distancelonger than the predetermined basic at-stopping inter-vehicle distancewhen the stop position of the host vehicle is within a rearward stoplimit area set behind the crossing lane.